Effectiveness of physiological traits in adopting safflower (Carthamus tinctorius L.) genotypes to water deficit condition

Abstract

Water deficit is the most limiting factor for seed yield of crop species in the arid and semi-arid regions. Due to increasing limitation of fresh water resources and importance of safflower (Carthamus tinctorius L.) as a significant oilseed crop in Iran, it is necessary to evaluate physiological responses of drought tolerance and its association with seed yield of this crop in water stress condition. In this study, 21 safflower genotypes were planted by hand in the field under water stress and non-stress conditions in a randomized complete block design with two replications during 2 years (2016–17). The results indicated that water deficit stress significantly reduced relative water content (RWC), chlorophyll a (Chl-a) and chlorophyll b (Chl-b) concentrations and seed yield, but increased ascorbate peroxidase (APX) and peroxidase (POX) activities and leaf proline concentration. Significant differences were observed among the genotypes for all studied traits except Chl-b concentration. Genotypes were discriminated according to their response to drought using stress tolerance index (STI). Drought tolerant genotypes displayed a higher capability for accumulation of proline in association with maintaining RWC, antioxidant enzymes activity and higher seed yield, compared to the drought sensitive genotypes. Presented results suggested that safflower genotypes with higher levels of antioxidant enzymes activity, RWC and proline accumulation are characterized by a higher STI. Therefore, these physiological traits can be employed as effective criteria for selecting safflower genotypes with more tolerance to water deficit stress.